1. Field of the Invention
This invention relates to a projection inspecting machine, in which an image to be measured can be projected onto a screen for observation inspection and in which the image to be measured can be observed more correctly through a microscope.
2. Background of the Prior Art
There has been known a projection inspecting machine. In this conventional inspecting machine, a projection lens mount attaching base is disposed above a table capable of moving two-dimensionally. This table serves to support an object to be measured placed on it. A projection lens mount attaching base constitutes a part of a projection optical system and is served as a base to which a projection lens is to be attached. An observation inspection is carried out by observing an image of the object to be measured, the object projected, in an enlarged scale, onto a screen by means of emission of an illumination light through a projection optical system.
In this conventional projection inspecting machine, it is an important point that an observation inspection is carried out rapidly and correctly with respect to the object to be measured based on the image thereof. To this end, attention is paid to a method as to how to improve the projection accuracy of an image of the object to be measured onto the screen. However, much difficulty is encountered. The reason is that some objects have surface colors and shapes which are difficult to be shown as an image. Examples of such colors and shapes are black, mat-finished plastic step, R surface, and the like. Since there is limit in intensity of illumination, resolution, transmission factor, etc., if the object to be measured has such unfavorable colors and/or shapes, the conventional projection inspecting machine has difficulty in exhibiting its measuring function to the full extent.